The present invention relates to an air bag assembly installed in a vehicle for restraining an occupant from forward movement in the event of collision of the vehicle, and including a gas generator for generating gas and a bag to be inflated by the gas. More particularly, the present invention is concerned with an air bag assembly of the type directing gas jetting out of the gas generator in a direction perpendicular to a direction which extends toward an occupant.
Various kinds of devices have heretofore been proposed for protecting an occupant of a vehicle against injury by physically restraining the occupant's body when the vehicle encounters a collision. An air bag assembly which belongs to a family of such devices is generally made up of a sensor responsive to decelerations of the vehicle greater than a predetermined deceleration, a gas generator for generating gas, and a bag connected at its base portion to the gas generator to be inflated by the gas. When the sensor senses a deceleration greater than the predetermined deceleration, a gas generating agent confined in the gas generator is fired to generate gas so as to inflate the bag. Such an air bag assembly may be positioned at, for example, a central part of a steering wheel or a lower part of an instrument panel to protect an occupant of a front seat or at the back of the seat back of a front seat to protect an occupant of a rear sheet. In the event of collision, the bag is inflated toward the occupant to restrain him or her from forward movement.
In the air bag assembly, should the gas jetting out from the gas generator be directed toward the operator, the bag would be rapidly inflated toward the occupant applying an intense impact to the occupant whose body tends to move forward by inertia. In light of this, it has been customary to form openings through a side or circumferential wall of a gas generator, so that gas may be blown off perpendicularly to the direction extending toward an occupant. Such a configuration is shown in Japanese Patent Publication No. 53-21779 and others. Specifically, in such a configuration, the bag is inflated sideways first freeing an occupant from a critical degree of impact.
A problem with the above-stated configuration is that the gas jetting out of the gas generator directly impinges on the base portion of the bag and, in addition, the temperature of the gas just blown off is extremely high due to the explosion of the gas generating agent. The high temperature gas hits against the base portion of the bag directly and continuously.
The bag of such an air bag assembly is usually constructed with a fabric which is coated or impregnated with rubber or synthetic resin for guaranteeing softness and air-tightness. The strength of such bag, is reduced by the hot gas which continuously impinges against the bag. Moreover, the base portion of the bag, directly affected by the hot gas is the portion which develops a considerable degree of stress when the bag is inflated. Because the pressure inside the bag is elevated when the occupant's body collides against the bag being inflated, a considerable stress is developed in the base portion. Hence, as the strength of the base portion of the bag is lowered by the hot gas, the occupant's body colliding against the bag is apt to blow a hole through the base portion or even tear it up.
To accommodate such a stress, there has been proposed to use a reinforcing member formed of cloth or the like, such as disclosed in, for example, Japanese Laid-Open Utility Model Publication (Kokai) No. 52-119234. Such reinforcing member, however, cannot cope with the hot gas satisfactorily partly because it is made of the same material as the bag and partly because it is simply put on and joined with the base portion of the bag.